The Vietnamese word "đầu lòng" means "elder" or "eldest" when referring to children in a family. It is used to identify the firstborn child among siblings.
Ông ta có hai con, đứa đầu lòng là con gái.
(He has two children, the elder of whom is a girl.)
Gia đình có ba con trai, đứa đầu lòng lên mười.
(There are three boys in that family, the eldest of whom is ten.)
In more formal or literary contexts, "đầu lòng" can be used to express pride or significance associated with being the firstborn, as the first child often carries certain familial expectations or responsibilities.
While "đầu lòng" primarily refers to the eldest child, in some contexts, it can also imply a sense of leadership or precedence in other areas, but this usage is less common.